The impact of cats and foxes on the small vertebrate fauna of Heirisson Prong, Western Australia. II. A field experiment

Abstract

The hypothesis that predation by feral cats
and introduced foxes reduces population sizes of small, native vertebrates was
supported by results of a predator-removal experiment at Heirisson Prong, a
semi-arid site in Western Australia. The methods of control used against cats
and foxes to protect native mammals reintroduced to Heirisson Prong produced
three broad ‘predator zones’: a low-cat and low-fox zone, where
foxes were eradicated and spotlight counts of cats declined after intensive
cat control; a high-cat and low-fox zone where spotlight counts of cats
increased three-fold after foxes were controlled; and a zone where numbers of
cats and foxes were not manipulated. Small mammals and reptiles were monitored
for one year before and three years after predator control began. Captures of
small mammals increased in the low-cat and low-fox zone, but where only foxes
were controlled captures of small mammals declined by 80%. In the
absence of cat and fox control, captures of small mammals were variable over
the sampling period, lower than where both cats and foxes were controlled, yet
higher than where only foxes were controlled. The capture success of reptiles
did not appear to be related to changes in predator counts. This study
presents the first experimental evidence from mainland Australia that feral
cats can have a negative impact on populations of small mammals.